Heart beat indicator



Aug. 6, 1957 K. w. EDMARK, JR

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571p (name: CONDENSER CL? KARL l4- EDMARKJR MAM 4M A rron NE United States Patent HEART BEAT INDICATOR Karl W. Edmark, Jr., Brookline, Mass., assignor to Physio Control Company, Inc., Brookline, Mass, 2 corpora tion of Delaware This invention relates to heart beat indicating apparatus, and more particularly to an electrical apparatus for simultaneously providing a positive, highly visible heart beat indication and an accurate indication of the heart beat rate of a patient to whom it is attached.

A main object of the invention is to provide a novel and improved apparatus which may be attached to a patient undergoing surgery or the like, to provide an instantaneous and constant visual indication of the heart rate and rhythm of the heart action of the patient.

A further object of the invention is to provide an improved apparatusfor use in simultaneously providing a positive visual indication of the heart action of a patient undergoing surgery or other medical procedure, and of the heart rate of the patient, said apparatus being simple in construction, being reliable in operation, and providing an unmistakable and highly visible indication of the patients heart action.

A still further object of the invention is to provide a compact and easily viewed instrument forindicating the heart action and heart beat rate of a patient undergoing surgery or the like, said apparatus being easy to attach to a patient, providing a heart action indication which is visible from a considerable distance, and being highly sensitive.

A still further object of the invention is to provide a combined heart beat and heart rate indicator which gives constant and instantaneous information of the heart rate and rhythm of a patient while the patient is being induced into or is under anesthesia, or is undergoing a procedure wherein it is important for the persons attending to notice rapidly any change in rate or rhythm of the patients heart action, and enabling the anesthetist or surgeon to be rapidly aware .of, and thus to treat, any sudden change in the heart rate or rhythm of the patient.

A still further object of the invention is to provide an improved electrical heart beat and heart rate indicator which utilizes an improved method of placement of the input electrodes, whereby an input signal of greater clarity and much greater amplitude is obtained than in the electrical devices heretofore employed for this purpose.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure 1 is a schematic wiring diagram of an improved combination heart beat and heart rate indicator according to the present invention, showing the method .of applying the electrodes to the body .of a patient.

Figure 2 is a front .elevational view of the main portion of an improved combination heart beat and heart rate indicator according to this invention.

Figure 3 is a side elevational view of the instrument of Figure 2.

Figure 4 is a group of typical curves showing how input signals of substantially increased amplitude are ob tained by employing the improved electrode placement of the present invention and showing wave forms generated by the input signals at various stages of the circuit.

Referring to the drawings, and more particularly to Figure 1, 11 designates a small electrode which is attached to the front of the chest of the patient, shown at 12. The electrode 11 may be fastened in any suitable manner'to the patients chest, or may comprisea needle inserted just under the skin. Designated at 13 is a relatively large grounding electrode which is placed on the back of the patient opposite the small electrode 11, as shown. The large electrode 13 may be fastened in any suitable manner to the patients back.

Designated at 14 is a shielded cable having the center conductor 15 and the outer shield 16. Electrode 11 is connected to center conductor 15 and electrode 13 is connected to shield 16. Shield 16 is connected to the instrument ground, as shown, by a conductor 17. Thus, electrode 13 and the patients body are maintained at the instrument ground potential.

The center cable conductor 15 is connected through a coupling condenser C1 to the grid 18 of a pentode V1 operating as a class A2 amplifier.

1n the input portion of the instrument, tubes V2 and V3 are also provided, said tubes being twin triodes operating as cathode follower amplifiers. High-mu triodes are preferably employed, which afi'ord high amplification and at the same time, extreme stability because of the inherent negative feed-back due to the high values of cathode resistance characteristic of the circuit.

As shown, the plate 19 of tube V1 is connected through a plate resistor R3 to a wire 20, which is in turn connected through a resistor R4 to a plate voltage supply wire 21. The screen 22 of tube V1 is connected through a screen resistor R2 to the wire 20. The cathode 23 is connected to the instrument ground wire 24. A grid resistor R1, is connected between grid 18 and ground wire 24. A grid by-pass condenser C2 is connected across resistor R1.

Plate 19 is connected through a coupling condenser C3 to the input grid 25 of tube V2. connected between grid 25 and ground wire 24. A bypass condenser C4 is connected across grid resistor R5. Cathode 26 of tube V2 is connected to ground wire 24 through a cathode resistor R6. Plate 27 of said tube is connected to plate supply wire 21 through a plate resistor R7.

Plate 27 is connected to the grid 28 of the second triode section of tube V2 by a wire 29. The cathode 30 of said second section is connected to ground wire 24 through a cathode resistor R8. The plate 31 of said second section is connected to plate supply wire 21 by a wire 32.

Cathode 30 is connected through a coupling condenser C5 and the resistance element of a potentiometer R9 to the ground wire 24. The adjustable contact 33 of po- .tentiometer R9 is connected to the grid 34 of the first section of tube V3. The cathode 35 of said first section is connected through a cathode resistor R10 to ground wire 24. The plate 36 of said first section is connected through a plate resistor R11 to the plate supply wire 21. Plate 36 is connected by a wire 37 to the grid 38 of the second section of tube V A by-pass condenser C6 is connected between grid 38 and ground wire 24. Cathode 39 of said second section is connected through a cathode resistor R12 to ground wire 24. Plate 40 of said second section is connected to plate supply wire 21 by a wire 41.

Cathode 39 is connected through a coupling condenser $7 to the input grid 42 of a twin triode indicator tube The voltage gain of the amplifier thus far described is of the order of 5000.

Referring to Figure 4, a typical input wave form across grid resistor R1 from a human heart using the electrode arrangement of the present invention is shown at B. Desi-gnat-ed at A is the wave form which is developed when A grid resistor R5 is wrist electrodes are employed, as in previous arrangements. By employing the electrode arrangement of the present invention, a deep negative S wave spike, shown at 43, is developed, not obtained when wrist electrodes are employed, the corresponding negative spike 44 of curve A belng relatively small in amplitude as compared with negative spike 43. By using the negative spike 43 as the rate-determining impulse, interference is eliminated from the P and T portions of the waves, shown in curves A and B.

in curve A, using wrist electrodes, it is necessary to use the positive R pulse-s as the ratedetermining signals, whereby interference is present from the P and T portions of the waves.

In the circuit of the present invention, the negative S Wave form elements from the heart are amplified to trig= ger the beat indicator, and this amplified S wave at the output of the amplifier (across resistor R12) is shown at 45 in the wave form curve C of Figure 4. With the sensitivity control R9 set at maximum, the average peak of the amplified S wave elements 45 from a normal heart is about 7.5 volts.

It will be seen that the negative input spikes 43 of curve B of Figure 4 have been amplified and converted to the positive wave form peaks 45 of curve C, appearing across resistor R12. 1 The positive spikes 45 may vary from about plus 3.0 volts to plus 10.0 volts, and are fed across a grid resistor R13 connected be-tween grid 42 of tube V4 and ground wire 24. A by-pass condenser Cs is connected across resistor R13.

The plate 83 of the input section of tube V4 is connected to a plate voltage supply wire 84 through a plate resistor R15. The cathodes 85 and 46 of tube V4 are connected to ground wire 24 through a variable bias resistor R14.

Plate 83 is coupled to the grid 47 of the second section of tube V4 through a condenser C9. The plate 48 of said second section is connected to wire 84 through a plate resist-or R111. A grid resistor R17 is connected between grid 47 and the cathodes 85, 46. A condenser C is connected between grid 47 and ground wire 24. Grid 47 is connected to the plate supply wire 84 through a relatively high resistance R which is of the order of one megohm.

Plate 48 of tube V4 is connected through a resistor R19, a wire 49, and a neon lamp 50 to ground wire 24. A condenser C11 is connected across neon lamp 50, as shown.

The positive wave C of Figure 4, when fed across resistor R13 produces a constant-shaped positive wave D (Figure 4) over a range of zero to 200 beats per minute. The voltage across the neon lamp 50 is maintained at a relatively low level of about plus 30 volts, with a supply voltage of about 250 volts on wire 84, by biasing grid 47 positive by means of resistor R15. This reduces the internal resistance of the second section of tube V4 to a level where a voltage drop of about 210 volts occurs across resistor R18. This'enables neon lamp 50 to be off at the zero signal levels. Resistor R14, employed as a common cathode bias resistor, controls the trigger level of tube V4, and by this means, the cathode bias is maintained at a sufficiently high level to keep the circuit from going into a slow self-oscillation, which it is capable of doing at low bias levels. Through the system of bypassing by the condensers C8, C10, and C11, the system is not affected by 60 cycle interference, other than to increase its sensitivity, which can be controlled by adjusting the potentiometer R9.

The time constant t of the wave form across condenser C11 and neon lamp 50 (.see curve D, Figure 4) is controlled by the RC network R15, C9, and is adjusted to give a light flash which roughly corresponds with the duration of the systolic (first) heart sound at normal heart rates. In operation, this is approximately 0.1 second.

Condenser C10 and resistor R17, in addition to bypassing 60 cycle interference, have a stabilizing influence on the modified univibrator circuit defined by tube V4.

Plate resistors R15 and R18 are chosen to provide the most stable circuit. If they are too low in value, the circuit goes into self-oscillation, and if they are too high, a short weak blink is produced by the neon lamp 50, which is not desirable from a clinical standpoint. R15 should be of the order of 220,000 ohms and R18 should be of the order of 150,000 ohms.

A double diode V5 is employed in conjunction with a condenser C15 and a battery 51 as a step charging circuit to actuate a rate meter circuit including the microammeter 52. As shown, one cathode 53 and one anode 54 of tube V5 are connected together and are coupled to Wire 49 through a coupling condenser C12. The anode 55 of the first section of tube V5 is connected to the negative terminal of battery 51. The positive terminal of said battery is connected to a wire 56. Condenser C13 is connected between the cathode 57 of the second section of tube V5 and wire 56. Connected in series across condenser C13 are the resistors R20 and R21. The junction of said resistors is connected to the input grid 58 of a double triode Vs through a resistor R22. A by-pass condenser C14 is connected between grid 58 and wire 56;

The anodes 59 and 60 of tube V5 are connected by a wire 61 to the plate voltage supply wire 21. A resistor R27 is connected between wire 61 and Wire 56. A resistor R25 is connected between wire 56 and ground wire 24. The grid 62 of the second section of tube V6 is connected to wire 56 through a grid resistor R26 of relatively high value. Connected in series across the cathodes 63 and 64 of tube Vs are the variable resistance R23 and the microammeter 52. Also connected across said cathodes is the resistance element of a potentiometer R24. The adjustable contact of said potentiometer is connected to ground through a bias resistor R25.

It will be seen that double triode V5 is thus employed in an electrometer circuit with microammeter 52, which gives a nearly linear heart rate indication from Zero to 200 beats per minute. Linearity is controlled by the choice of proper values for the condensers C12, C13, the resistors R20, R21, and the negative bias source, battery 51. The electrometer circuit is adjusted to give full scale deflection with a positive voltage of about 1.5 volts applied to the grid 58 of the first section of tube V5 by means of the variable resistance R23. Zero adjustment is obtained by adjusting the contact element 65 of potentiometer R24.

The curve E of Figure 4 shows the wave form across the step charge condenser C15. As shown by this curve, the charge on condenser C13 is built up in steps derived from the successive positive pulses, shown at 72, developed across the neon lamp 50, said positive pulses causing lamp 50 to conduct with each heartbeat, since with a normal heart signal, the amplitude of the pulses 72 is sufiiciently great to ionize the gas in lamp 50. Each pulse 72 causes a current pulsation in the circuit comprising cathode 53, anode 55, battery 51, resistor R21, resistor R20, cathode 57 and anode 54. Normally (in the absence of the pulses 72) battery 51 places a negative bias on anode 55 of tube V5 which is sufficient to prevent any thermionic-emission flow of current through the circuit comprising cathode 53, anode 55, battery 51, resistor 21, resistor 20, cathode 57, and anode 54. This maintains grid 58 of tube V5 at zero reference voltage with respect to wire 56. The potentiometer R24 is adjusted to give a zero indication on microammeter 52. When current pulsations are produced in tube V5, the current through resistors R21 and R20 is in a direction to make grid 58 positive, removing the normal negative bias thereon. The current pulsations through resistors R21 and R20 produce steps 73 of charge on the condenser C13, said condenser discharging at a relatively slow rate through said resistors during the intervals between pulses 72. The equilibrium charge level on condenser C12 is reached after a few pulses 72, said: equilibrium charge level being in accordance with the frequency of the pulses 72. Since this charge level provides the positive voltage on grid 58,

the deflection of the electrometer microantmeter 52 will be inaccordanee with the pulsefrequency.

It will be further noted that tube Va is connected in a bridge circuit and that the bridge becomes unbalanced when the voltage on grid 58 is changed from the null value thereof. Normally, namely, at balance of the bridge, grids 58 and 62 are at relative potentials such that no current flows through, the circuits connecting the cathodes 63 and 64. I

The power supply employed is conventional in design and comprises a power transformer T1, 21 full-wave rec: tifier V7 and a double-section filter network consisting of inductances L1, L2, and filter capacitors C15 and C16, con nected as shown. This provides approximately 250 volts across a bleeder resistor R29 with a ripple component of about 0.012%. Additional regulation isobtained by the use of a dropping resistor Rae and a voltage regulator tube V8, to provide a constant voltage source of 145 volts to wire 21 (to the amplifier and electrometer circuits) over a wide range of varying line voltage conditions, adding to the stability and accuracy of the entire circuit.

The main control switch 66 of the power supply is mechanically coupled to the adjustable element of the sensitivity control R9 so that a single knob may be employed to energize the instrument and to control its sensitivity.

The instrument is contained in a metal housing 67, shown in Figures 2 and 3. The front wall of the housing has the sloping upper portion 68 on which are mounted the microarnmeter 52 and the neon lamp 50 in side-byside adjacent relationship, so as to be easily viewed simultaneously, so that the flashing of theneon lamp and the indication of the meter 52 maybe observed at the same time. The housing has the vertical lower front wall portion 69 on which is mounted a cable connector 70 to which the cable 14 may be connected, and the sensitivity control potentiometer R9, said potentiometer being provided with the instrument control switch 66, as above described, which is operated by the knob of the potentiometer. The side walls of the housing 67 are provided with suitable ventilating louvers 71.

The following circuit values were employed in'a typical instrument constructed in accordance with the present invention:

RESISTORS R1 megohms 2.2 R2 ohms--. 100,000 R3 do- 220,000 R4 o-.. 150,000 R5 megohms 1.5 Re ohms-- 2,700 R7 do. 270,000 Ra do 270,000 R9 meg0hms; 2 R10 ohms 2,700 R11 do 270,000 R12 do 270,000 R13 do 270,000 R14 do 15,000 R15 do 220,000 R16 megohm 1.0 R17 ohms 560,000 R13 dO 150,000 Km d0... 39,000 R20 megohm 1.0 R21 do 1.0 R22 "ohms" 560,000 R23 dO.. 10,000 R24 10,000 R25 -do 47,000 Rzs megohms 1.5 R27 ohms 33,000 R211 "do"-.. 68,000 v sitter-s Rab 27,000 R30 d0 6,800

CAPACITORS Mfd. C1 l 1.0 Ca .05 C3 1.0 C4l .05 C5 1.0 Cs .05 C7 1.0 Ca .25 C9 1.0 C10 .25 C11. 1.0 C12 .005 C13 1.0 C14 1.0 C15 20.0 C16 20.0

' TUBES V1 6AU6 V2 12AX7 V3 12AX7 V4 12AU7 V5 5 6H6 V6 12AU7 V'r 6X4 INDUCTORS L1 microhenries 8.5 L2 "do..." 8.5

TRANSFORMERS T1 650 V. CT

While a specific embodiment of an improved heart beat indicator and heart rate counter has been disclosed in the foregoing description, it Will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. Apparatus for utilizing the negative S pulse of the heart action wave of a patient to provide simultaneous heart beat visual signals and heart beat rate indications comprising a first electrode adapted to be positioned on the front of the chest of a patient, a second electrode adapted to be placed on the patients back, an amplifier circuit arranged to provide a positive output signal in response to a negative input signal furnished thereto, means connecting said electrodes to the input of said amplifier circuit, a neon lamp, means connecting said neon lamp to the output of said amplifier circuit, a condenser, means charging said condenser simultaneously with the application of output voltage from said amplifier circuit to said neon lamp, a meter, and means connecting said meter to said condenser and being arranged to provide a reading on said meter in accordance with the frequency of the negative S pulses.

2. Apparatus for utilizing the negative S pulse of the heart action wave of a patient to provide simultaneous heart beat signals and heart beat rate indications comprising a first electrode adapted to be positioned on the front of the chest of a patient, a second electrode adapted to be placed on the patients back, an amplifier circuit arranged to provide a positive output signal in response to a negative input signal furnished thereto, means connecting said electrodes to the input of said amplifier circuit, a voltage-responsive intermittent signal device, means connecting said signal device to the output of said ampli fier circuit, a pair of diodes, means connecting the cathode of one of said diodes and the anode of the other diode as oneao 1 a 7 to one terminalof said signal device, and a rate indicating circuit connected to the anode of said one diode and the cathode ofthe otherdiode.

3. Apparatus for simultaneously providing a flashing visual signal in synchronism with the heart beats of a patient and for indicating the rate of such heart beats comprising in combination a neon lamp, means'for conductively energizing said lamp in response to a heart beat signal of predetermined amplitude, a pair "of diodes, a rate indicating circuit, means connecting the cathode of one diode and the anode of the otherdiode'to one 'terminal of the neon lamp, and circuit means connecting the rate indicating circuit between the anode of said "one diode and'the'cathode of said other diode and'b'eing formed and arranged to provide an indication in accordance with the frequency of energization of said neon lamp,

4. Apparatus for simultaneously providing a flashing visual signal in synchronism with the heart beats of a patient and for indicating" therate of such heart beats comprising in combination a neon lamp, means for conductivcly energizing said lamp in response to a heart beat signal of predetermined amplitude, a pair of diodes, means connecting the cathode of one of said diodes and the anode of the other diode to one terminal of said neon lamp, and a rate indicating circuit connected between the anode of said one diode and cathode of the other diode, said rate indicating circuit being arrangedv to pro vide an indication of the frequency of the energizing voltage applied to said neon lamp.

5. Apparatus for simultaneously providing a flashing visual signal in synchronism with the heart beats of a patient and for indicating the rate of such heart beats comprising in combination a neon lamp, means for'conductively energizing said lamp in responseto'a heart beat signal of predetermined amplitude, a pair of diodes, means connecting the cathode of one of ,said diodes and the anode of the other diode to one terminal of said neon lamp, a condenser connected in circuit with the anode of said one diode and the cathode of the other diode, a voltage indicating circuit connected across said condenser and having a terminal connected to the remaining terminal of the neon lamp, and means for charging said condenser in accordance with the frequency of the energizing voltage applied to said neon lamp.

6. Apparatus for simultaneously 1 providing an intermittent perceptible signal in synchronism with the heart beats of a patient and for indicating the rate of such heart beats "comprising in combination a signal device arranged to beenergized when a voltage exceeding a predetermined value 'isapplie'd th'ereto,'means for energizing said signal device in'response toa heart beat signal of predetermined amplitude, a pair of diodes, means connecting the cathode of onepfs'aid diodes and the anode of the other diode to' onejt'erminal ofsaid signal device, a condenser connectedin circuit with the anode of said one diode and the cathode of the other diode, a voltage indicating circuit connected across said condenser and having a terminal connected to the remaining terminal of said signal device, and means for charging said condenser in accordance with the frequency of the energizing voltage applied to said signal'devic'e.

7. Apparatus for simultaneously. providing an intermittent signal'in synchronism with the heart beats of a patient and for indicating the rate of such heart beats comprising in combination an indicating device, means for energizing said indicating device in response to a heart beat signal of predetermined amplitude, a pair of diodes, a rate indicating circuit, means connecting the cathode of one diode and the anode of the other diode to one terminal of the indicating device, and circuit means connecting the rate indicating circuit between the anode of said one diode and the cathode of said other diode and being formed and arranged to provide an indication in accordance with the frequency of energization of said indicating device.

8. Apparatus for'simultaneously providing an intermittent signal in synchronism with the heart beats of a patient and for indicating the rate of such heart beats comprising in combination an electrical indicating device, means to energize said indicating device inresponse to a heart beat, a pair of diodes, an electrical rate indicator,

means connecting the cathode of one diode and the anode of the other diode to one terminal of the indicating device, and circuit-means connecting the rate indicator between the anode of said one'diode and the cathode of said other diode and being formed and arranged to provide an indi-' cation in accordance with the frequency of energization of said indicating device.=

References Cited in the file of this patent UNITED STATES PATENTS Sturm Apr. 13, 1948 

